This invention relates to the production of arylene sulfide polymers. In one of its aspects this invention relates to a novel method for producing novel arylene sulfide polymers, and to the polymers themselves. In another of its aspects this invention relates to producing arylene sulfide polymers of higher molecular weight than are produced without using a multiple dehydration method with the same starting materials.
The preparation of arylene sulfide polymers having higher molecular weight as evidenced by lower melt flow without curing the polymers as compared to arylene sulfide polymers known in the art is of particular interest since lower melt flows, particularly within the range of 1 to 700 as determined by the method of ASTM D 1238-70, are particularly useful in the production of fibers, molded objects and filaments since the usual curing step is obviated.
In the production of an arylene sulfide polymer by employing a p-dihalobenzene, an alkali metal sulfide, lithium acetate, an N-alkyl-2-pyrrolidone, and optionally a polyhalo aromatic compound having more than two halogen substituents per molecule, the lithium acetate is generally used as the dihydrate, and the alkali metal sulfide is generally employed as a hydrate and/or in admixture with free water. For example, it is convenient to use the alkali metal sulfide in the form of a composition comprising about 45 to about 50 weight percent sodium sulfide, expressed as Na.sub.2 S, this composition being prepared from aqueous sodium hydroxide and aqueous sodium bisulfide, both commercially available. However, it is preferable that water be removed from both the lithium acetate dihydrate and the alkali metal sulfide in hydrated form and/or in admixture with free water prior to contacting the p-dihalobenzene and the polyhalo aromatic compound having more than two halogen substituents per molecule, if used, with the other ingredients employed in the production of the polymer. Although water can be removed from a mixture of the lithium acetate dihydrate and the alkali metal sulfide in hydrated form and/or in admixture with free water, in an N-alkyl-2-pyrrolidone, by distillation in a one-step dehydration, the present invention utilizes a two-step dehydration process which provides the advantages of producing polymers of lower melt flow than are produced when a single step dehydration is employed.
It is therefore an object of this invention to produce arylene sulfide polymers of increased molecular weight as compared to those produced by prior art methods.
Other aspects, objects and the various advantages of this invention will become apparent upon reading this specification and the appended claims.